This invention relates to novel gas valve control housings for use in the consumer, commercial, and industrial product markets.
Long known for controlling gas flow, gas valves have been in use for decades to control flow of a variety of gaseous fuels for appliance products. Such valves are used to regulate flow and pressure of natural gas and propane, for example, in residential consumer appliances such as central heating units, space heaters, wall heaters, water heaters, boilers, stoves, and outdoor grills. Additionally, gas control valves are widely used in commercial and industrial applications.
Gas valves operate to regulate the flow of gas from a pressurized source to, for example, a downstream gas burner. Simplistic gas valves may provide only manually operated open and closed functions. More sophisticated gas valves, however, may include additional regulation features such as low, medium, and high flow stops and may include thermostatically controlled servo motor actuation, inlet and outlet screens, and bleed gas and pilot filters.
To adequately control gas at a variety of incoming pressures, modern gas valves require a number of components to become effectively and conveniently operational. Gas valve assemblies at a minimum usually require a valve stem, a valve guide, a valve seat, an actuator rod, an actuator knob, an inlet means to connect to the gas supply, and an outlet means to connect to the burner. Such assemblies may also employ gas tubing for a pilot, and pressure sensing diaphragms, magnetic structures, and servo-actuators to thermostatically control the valve.
Typically, a valve assembly is packaged in a housing to contain and support the discrete components of the assembly and to provide a structural fixture from which the valve can be mounted to the appliance. Valve assembly housings have been configured for these purposes and are frequently formed from metal alloys. Aluminum and stainless steel have been materials of choice for such control housings.
The metal housing is often cast to form two mating parts and is subsequently machined to provide precision orifices and other intricate features such as seats for press fitting of the valve components. Gas transport passageways between components are also precision machined into one or more of the housing parts. Gaskets are configured between the mating surfaces of the housing parts before they are joined to prevent gas leakage after assembly. Gasket material is also used to seal component parts to the housing.
The metal housings of the prior art are typically cast from dies. Such metal cast housings, frequently composed of aluminum, may be gas permeable, the composition of the cast part being somewhat porous. As is frequently the case, the inside of the valve assembly housing is pressurized from the gas source creating a pressure differential between the inside and outside of the housing. The porous cast metal housing wall and/or incomplete sealing of mating surfaces may form pathways for undesirable leakage.
Control valve housings are often subject to consumer environmental requirements such as AGA, CGA, and Underwriters Laboratories (UL). Valve assemblies may, for example, be subject to temperature ratings of between xe2x88x9240 degrees Fahrenheit to +175 degrees Fahrenheit. Temperature-induced expansion and contraction of the porous cast metal may also cause a pressure differential to form, further facilitating undesirable transmission of the gas through the porous housing wall and/or through pathways formed by incomplete sealing of housing and component parts.
One method to streamline manufacturing of valve assemblies, has been to adopt a single valve assembly housing to accept a variety of valve components. In this fashion, a variety of valve models from the simplistic to the complex can utilize the same cast housing parts. Press-fit orifices and gas flow passageways can be machined and changed as needed depending upon the configuration of the valve assembly to be inserted. To accommodate a simple valve assembly, for example, only a small number of press-fit orifices and gas transport passageways are required to be machined. To produce a more complicated valve assembly, additional machining to the housing may be required to provide for the extra components and to provide functional communication, such as gas transport passageways, therebetween.
Varying processes to construct a product line from a single metal housing configuration can be costly as each housing must be machined to suit a particular model and its particular componentry. Shifting from one machining procedure to another requires manufacturing set-up adjustments thereby adding time and expense to modify each housing. Additionally, the handling of non-uniform parts, due to changes in manufacturing procedures from one model to the next, may serve to increase the likelihood of error by operators of the machining tools producing the specialized housings.
Another way in the prior art to provide reduced-cost manufacturing of valve control assemblies has been to create a standardized housing that accommodates components of a variety of valve models. The housing is formed to accommodate the most complicated assembly contemplated for the housing, and is machined in the same fashion for all models. Models not requiring all the componentry of the most sophisticated design may be configured with dummy non-functioning components. Alternatively, undesired components and their facsimiles may be omitted altogether depending on the configuration. However, the unnecessary machining required of the housing for simplified models and dummy parts is costly and wasteful. Utilizing this approach, valve controls of basic design are packaged in housings that may be of unnecessarily excessive size, weight, and cost.
Cast metal housings of the prior art suffer from additional cost disadvantages. During the molding process, dies that form metal parts frequently wear relatively rapidly. Increased wear of a die diminishes the number of dimensionally conforming parts produced from that die. Yielding fewer conforming parts, the costly die must be replaced frequently. Furthermore, the weight of the cast metal housing is typically relatively heavy resulting in increased transportation costs to ship the valve control, whether in unfinished or in fully assembled form.
Competition in the valve control markets is substantial. Lowering costs of production in the valve control industry, whether it be in materials, numbers of parts, processing, or otherwise is actively sought out by manufacturers to provide themselves with a competitive advantage. Such advantage may take the form of lowered costs which translate into increased market share, and, ultimately result in increased return on investment.
As valve control assemblies often require a substantial number of discrete parts, cost disadvantages to the manufacturer can quickly multiply. To produce a product line of control valves often requires stocking, compiling, and assembling large numbers of parts increasing numbers of discrete parts also provides for increased opportunities for error, manufacturing time lost, material scrap, and increased product returns.
What is needed is a valve control housing that is light-weight, does not leak, requires less time to manufacture, and is economical to produce and transport. The present invention fulfills this need.
This invention is directed to an improvement in valve control housings, specifically those used in the consumer, commercial, and industrial markets to house gas control valves. The present invention includes a plastic molded body sealingly surrounded by an outer metal case. The plastic body is molded to accept valve components and includes necessary gas transport passageways and an integral over-molded rubber sealant. The outer metal case is formed from an extruded metal tube capped at each end by a metal plate.
The molded plastic body is modular in design so as to provide for varying functional components, and has an over-molded rubber seal integral to it for sealing against the metal case so as to prevent undesirable leakage of gas. The plastic body fits into the extruded metal tube and is secured at the top and bottom by metal plates.
The present invention includes a plastic body molded in a fashion so as to accept valve components necessary for operation of the particular valve model. A variety of plastic body configurations may be produced by utilizing various modular injection molds or, alternatively, produced from a single mold encompassing an entire body.
While varying internally, depending on the model, the exterior dimensions of the plastic body is formed to be sealingly encapsulated by the metal case. An integral rubber seal is molded over the plastic body to help prevent gas from undesirably leaking into the exterior environment. By varying the internal configuration of the plastic body via selection of injection mold, the problem of high costs associated with casting and individually machining metal housing is eliminated. In addition, the present invention possesses a number of advantages over prior art configurations used throughout the gas control valve industry.
One advantage of the present invention is the modularity of the plastic body. Many different body configurations can be produced in the plastic body to fit in the same extruded metal casing, providing many different functions including, but not limited to, direct opening, intermittent pilot, provisions for side outlets, non-regulated configurations, etc. The present invention reduces the cost of producing many different models in a single product line of controls.
Many changes to the operability of the valve controls can be made in the mold for the plastic body without requiring changes in the assembly or the pieces used for the assembly of a particular operation outside the control housing. Additionally, certain components can be eliminated by incorporating them into the plastic body such as valve seats and seals. Reduced componentry provides for simplified assembly and fewer rejected parts due, for example, to out of order installation. Many internal chambers and passages as well as additional components are provided for by way of differing molds for the plastic body. Thus, a base model housing may not require additional complexity to provide for alternate versions of the control. More sophisticated valve control assemblies may be provided in a plastic body of the same external dimensions so as to fit within the metal casing.
Another advantage of the present invention occurs in the extended life of the die used to mold the plastic body. This advantage is found in the comparative cost, wear, and useful life of utilizing plastic instead of metal injection molds. Plastic components produced through injection molding are less costly than the same configuration as produced in a metal die due to the extra wear caused to the die by the injection of metal during the molding process. The tooling necessary for the plastic injection also lasts longer than similar equipment used for metal parts and produces more dimensionally accurate parts over a longer period of time.
Still another advantage of the present invention is that little or no machining is required in the plastic body. In the prior art, precision orifices and many other intricate features must be machined into a metal casting for the production of a gas control. A plastic body may be molded into the desired configuration out of the mold with the required dimensional attributes for operability with little, if any, need to finish the body by way of machining. The present invention may eliminate the costly machining step in production of the valve control housing.
A further advantage of the present invention is the reduction in the number of parts required to produce the valve control. Many small internal components that previously would be assembled into a machined metal body with press fits can be integrated directly into the plastic body. The over-molded rubber seal on the plastic body, for example, can be integral to the plastic body, and can be formed in the same mold. Alternatively, a discrete seal may be utilized. The over-molded rubber seals should eliminate the use of gaskets. Valve stems, pressed-in orifice spuds, and valve seats and seals may also be integrated into the plastic body. Such integral components may be formed in the plastic body mold, sonically welded in, and/or over-molded to the plastic body.
A further advantage of the present invention is the reduced weight of the housing which is provided in large measure by the plastic body. Cast aluminum parts, for example, are substantially heavier than plastic injected parts of the same volume. A lighter weight control does not require as much mounting hardware as a heavier control, further reducing the weight of the end product. Lower weight translates into further reduced transportation costs and product costs.
Another advantage of the present invention is the elimination of the metal cast housing. The use of the extruded metal tube eliminates most of the inherent problems of porosity and potential leakage associated with cast metal parts. Use of the plastic body and over-molded rubber seal for the internal valve seats and gas passages should also reduce or eliminate the need for gaskets.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features of the invention.